1. Field of the Invention
The present invention relates to an optical measuring apparatus and an optical measuring method in which an object is illuminated with light, and light transmitted through or reflected from the object is measured.
2. Description of the Related Art
In an apparatus for measuring an amount of a substance by means of light measurement, an object under measurement which is horizontally placed is illuminated with light from a light source, light reflected from the object is converted into an electric signal by a light receiving device, the signal is converted to a logarithm to obtain the optical density value, and the amount of the object is obtained from the optical density value.
In an optical measuring apparatus for clinical examination, a slide in which a monolayer of a reagent is applied to a transparent support medium is used as an object under measurement, a liquid specimen such as blood is dropped on the slide, and a change of the optical density due to a reaction with the reagent layer is measured to obtain the optical density value. The optical density value is converted to a clinical value to attain a desired analysis.
In clinical examination or the like, it is required to measure the optical densities of plural components contained in blood. In an optical measuring apparatus, therefore, blood of the same person is dropped on plural slides to which different reagents are applied respectively, and the above-described measurement is conducted on each of the slides (for example, see JP-A-05-018895).
Usually, the amount of a substance is proportional to the optical density of the substance. By contrast, the common logarithm of the amount of light received by a light receiving device is proportional to the optical density, and hence the light amount is inversely proportional to the optical density. Depending on the component to be examined, namely, the amounts of light reflected from the slides are varied. In the conventional optical measuring apparatus, therefore, the light receiving device must have a wide dynamic range in which lights reflected from all the slides can be accurately received. A light receiving device having a wide dynamic range is expensive, and hence the production cost of the conventional optical measuring apparatus is inevitably increased.